The present invention relates generally to tuned dynamic absorbers and, in particular, to a steering wheel dynamic absorber assembly.
Tuned dynamic absorbers are well known. These absorbers function by adding a secondary mass or masses via attachment elements with spring-like and damper-like properties to a system having unwanted vibrations. The added mass or masses and attachment elements comprise the tuned dynamic absorber. The natural frequency of the absorber is equal or near that of the unwanted vibration in the original system and, through dynamic actions well known to those skilled in the art, the absorber suppresses unwanted vibrations at narrow frequency bands.
Periodic vibrations in moving vehicles, especially at tire-wheel rotation rates, have become particularly problematic over the last few years. In addition, other annoying vibrations occurring on irregular road surfaces frequently involve vibrations at the steering wheel. Unwanted periodic torsional steering wheel vibrations at the first order of the tire-wheel rotation rate (typically at highway speeds of 50-90 miles per hour), defined as smooth road shake, are prevalent on many vehicles. Other vibrations involving rim motions of the steering wheel, occurring during moving operation or, in the case of powertrain excitation, even stationary idle operation, are likewise annoying and have been observed on certain vehicles. One type of solution for periodic vibrations has been improved quality through component specifications designed to reduce the internal exciters, such as tire and wheel non-uniformity and imbalance tolerances. Other solutions have included dynamic tire and wheel assembly balancing and match mounting of the assembly components, which is the practice of preferentially aligning the relative orientation of the tire on the wheel for minimal net periodic force excitation.
Reducing periodic exciters through ever tightening component tolerances, however, has not been able to eliminate vibrations completely. In addition, vehicle modifications intended to reduce vibratory sensitivity have resulted in compromises in other performance areas, such as steering responsiveness in serpentine or cornering maneuvers.
The use of absorbers to suppress vibrations, in addition to tightening component tolerances, is a common practice by vehicle manufacturers. Specifically, in steering column applications, a common practice is to attach an absorber near the center of rotation of the steering wheel. These types of devices, however, have been used only for suppressing translational or out-of-plane modes of vibration at the steering wheel.
It is desirable, therefore, to utilize a tuned dynamic absorber to provide a cost-effective and relatively lightweight solution for suppressing vibrations at the steering wheel regardless of the mode of the vibration and, in particular, to suppress torsional vibrations of the steering wheel.